OTTAWA -- A large group of Canadian climate scientists, environment advocates, students and business owners want climate change to be the No. 1 issue for voters this fall.

A hundred of them signed an open letter to Canadians this week, urging them to take more time to understand the impacts of climate change and the solutions each party offers.

Merran Smith, executive director of Clean Energy Canada, says the political fight about the federal Liberals' carbon tax has become a distraction from the message Canadians should be getting: that climate change is the key issue of our time.

Smith says the science says humanity has three to four years to turn things around before we can no longer stop the planet from heating up catastrophically.

She says climate change also affects almost any other issue voters might care about, from health care to the economy to immigration.

In the letter, the advocates note Canadians produce two-and-a-half times more pollution per person than people in China, nine times more than people in India, and two to three times more than people in France, Germany, the United Kingdom and Japan.